mitt romney and president obama are preparing for the debate tomorrow night. the president has a four-point advantage going into this head-to-head match-up. it will focus on the economy and domestic issues. jan crawford is in denver this morning. >> reporter: both romney and the president have no more big campaign events before tomorrow night's event. last night here in denver, romney had a rally before more than 5,000 people. he picked up the endorsement of broncos legend john elway, but today they're getting ready. romney is here in denver and the president is in las vegas. less than 10% of vote who are are undecided who can say they've changed their minds. romney's challenge is to show why his proposal will make their life better. why the president doesn't deserve another chance. there was an interesting focus group in ohio this week with voters who backed the president in 2008, but they're not sold this time. and it shows some of them think the president just isn't to blame for the economy, and they also don't know a lot of good about romney, thanks to som